Spatial Lattice Modulation for MIMO Systems

TL;DR

This paper introduces spatial lattice modulation (SLM) for MIMO systems, leveraging multi-dimensional lattice points to enhance spectral efficiency and SNR gains over existing spatial modulation techniques, with analytical and simulation validation.

Contribution

The paper proposes a novel SLM method that exploits lattice structures for improved MIMO performance, including analytical expressions and a low-complexity detection algorithm.

Findings

SLM achieves higher spectral efficiency than existing methods.

Dense lattice SLM provides significant SNR (coding) gain.

Proposed detection method reduces complexity while maintaining performance.

Abstract

This paper proposes spatial lattice modulation (SLM), a spatial modulation method for multipleinput-multiple-output (MIMO) systems. The key idea of SLM is to jointly exploit spatial, in-phase, and quadrature dimensions to modulate information bits into a multi-dimensional signal set that consists oflattice points. One major finding is that SLM achieves a higher spectral efficiency than the existing spatial modulation and spatial multiplexing methods for the MIMO channel under the constraint ofM-ary pulseamplitude-modulation (PAM) input signaling per dimension. In particular, it is shown that when the SLM signal set is constructed by using dense lattices, a significant signal-to-noise-ratio (SNR) gain, i.e., a nominal coding gain, is attainable compared to the existing methods. In addition, closed-form expressions for both the average mutual information and average symbol-vector-error-probability (ASVEP) of generic SLM are derived under Rayleigh-fading environments. To reduce detection complexity, a low-complexity detection method for SLM, which is referred to as lattice sphere decoding, is developed by exploiting lattice theory. Simulation results verify the accuracy of the conducted analysis and demonstrate that the proposed SLM techniques achieve higher average mutual information and lower ASVEP than do existing methods.